Some applications in genomic analysis require the detection of copy number variation. Pre-natal screening, for example, may determine if certain portions of Chromosome 13, 19, and 21 are duplicated or deleted in fetal free floating deoxyribonucleic acid (DNA). One way to accomplish this is to enrich a whole genome sample for the specific regions on the select chromosomes (e.g., via PCR). PCR however can introduce bias or errors in the product in several different ways, including disparities between the rates of enzymes or differences between primer binding affinities to particular sites.